1. Technical Field of the Invention
The present invention relates to method and device in which a grinding wheel and an abrasive cloth are dressed using light.
2. Description of the Related Art
With the development of recent scientific technique, high accuracy is required also for processing technique. In the field of abrasive machining as well, the processing accuracy and the repeatability of processing become more important than ever. For example, polishing work is an indispensable technique as a CMP technique in the semiconductor manufacture process. As an important technique in the abrasive machining, a dressing technique as a means for stable processing while preventing a tool from being clogged can be exemplified. For the dressing technique, many means such as mechanical/electrical means, means using a laser, and the like have been proposed and are properly used according to the kind of a tool to be used or the like.
The mechanical dressing means uses a single dresser, a rotary dresser, or the like to mechanically remove a tool surface and perform dressing, and is used for many tools.
As electrical means, there are means for electrolyzing an electrically-conductive tool to melt a tool surface, means for discharging electricity to crush a tool surface by the energy, and the like. The electrical means is effective dressing means for a rigid tool such as a metal bond grinding wheel, which is difficult to be dressed, by the mechanical means.
The means using a laser is means for converging light energy by a high-output laser, irradiating a tool surface, converting the energy into thermal energy, and melting and removing the tool surface. It can be said that this dressing means can be applied to various tools.
Recently, besides these means, means for injecting a slurry, means using free abrasive grains, means for melting a bond material by a solvent, and the like have been developed and studied.
With respect to a resin bond grinding wheel, since the bond material is softer and has higher impact absorption than other metal bond grinding wheels, a soft workpiece is not easily damaged, and high-grade surface roughness can be realized. In the resin-bond grinding wheel containing fine abrasive grains, however, clogging easily occurs. When clogging occurs, the high-grade surface roughness cannot be realized.
Although a grinding wheel with a low degree of bond has been developed in order to prevent the clogging, there are problems such that the processing efficiency is low and it is necessary to design a grinding wheel with an optimum bond degree which does not cause breaking or clogging in accordance with the material of a workpiece.
The mechanical dressing method, the means for injecting slurry, the means using free abrasive grains, the means for melting the bond material by a solvent, and the like are difficult to be carried out when the controllability and automation of the dressing and in-process dressing are considered.
Since the metal bond grinding wheel is mainly used in the electrical dressing method, a soft material is easily damaged in the processing, and it is difficult to realize high-grade surface roughness. Moreover, since a bond material of metal is dissolved as a metal ion in the dressing operation, the method is not suited for processing of an electronic part, which is easily affected by a metal ion.
According to the dressing method using a laser, since a high-output laser is used, an expensive device is necessary. The maintenance cost is high, and handling is troublesome.